Tetracyanoquinodimethane good acceptor

Much work has been undertaken to modify electrode surfaces with films which are themselves conducting. The most promising approaches involve organic charge transfer and radical ion polymers. Coordination chemistry has, to date, played little part in this work (a good recent review is available),67 but one example relating to ferrocene chemistry can be quoted. In this example a well known electron acceptor, 7,7, 8,8 -tetracyanoquinodimethane (TCNQ 27), is modified and incorporated into polymer (28) in which the iron(II) of the ferrocene unit is the electron donor. The electrical conductivity of such a film will depend on partial electron transfer between ion and TCNQ centres as well as on the stacking of the polymer chains. The chemistry of other materials, based on coordination compounds, which have enhanced electrical conductivity is covered in Chapter 61. 

Bisbenzene chromium reacts with good 77-acceptor Lewis acids to form complexes (CgHg)2Cr L" (L = tetracyanoethylene, trinitrobenzene, -quinone, chloranil) in which electron transfer from the (CgHg)2Cr to the Lewis acid has taken place. The complexes are best described as bisbenzene chromium cation salts of radical anions (765). The crystal structure of one such compound [(MeCgHg)2Cr] (TCNQ) (TCNQ = 7,7,8,8-tetracyanoquinodimethane) has been determined and consists of Stacks of TCNQ anions and bisbenzene chromium cations with interplanar spacings of 3.42 A (577). 

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